3100 does not turn.

[sgchllngr]

Well, wife told me engine started knocking so she shut it off. I went out to restart and it would not turn, took a socket and tried to turn by hand, no-go. All I get is one revolution forward and one back, locks in same spot. What are the odds, either something came apart on top, or on bottom, which should I look at first?

[torq455]

might be a badly dammaged rod bearing and with the extra clearence, it might me hanging up on the block. had the same thing happen to a cierra 3.3. evetually did back and foruth by hand and got it to run again for a short trip to the junk yard. though, it's possible the cam may be frozen too. had to tell where to start looking. i'd take the oilpan off. it's easier than taking most of the top half of the engine apart just to look.